expr.cxx

eCos1.31版

    CYG_PRECONDITION_CLASSC(expr);
    CYG_PRECONDITIONC((CdlExprOp_Invalid == token) || (CdlExprOp_And == token));

    int current_subexpr = expr->first_subexpression;
    initialise_tokenisation(data, index);
    parse_expression(expr);
    if (CdlExprOp_And == token) {
        CdlSubexpression subexpr;
        subexpr.op        = CdlExprOp_And;
        subexpr.lhs_index = current_subexpr;
        subexpr.rhs_index = expr->first_subexpression;
        push_subexpression(expr, subexpr);
    }
    token       = token_to_expr_op();
    index       = token_start;
    token_end   = current_index;

    CYG_REPORT_RETURN();
}

//}}}

//}}}
//{{{  Expression Evaluation            

// ----------------------------------------------------------------------------
// Expression evaluation. This always happens in the context of a
// particular toplevel. The parsed expression is held in what amounts
// to a simple tree, so evaluation involves some recursion and a big
// switch statement.

static void
evaluate_subexpr(CdlEvalContext& context, CdlExpression expr, int subexpr_index, CdlSimpleValue& result)
    throw(CdlEvalException, std::bad_alloc)
{
    CYG_REPORT_FUNCNAME("evaluate_subexpr");
    CYG_REPORT_FUNCARG2XV(expr, subexpr_index);
    CYG_ASSERTC((subexpr_index >= 0) && ((unsigned int)subexpr_index < expr->sub_expressions.size()));

    const CdlSubexpression& subexpr = expr->sub_expressions[subexpr_index];
    switch(subexpr.op) {
    case CdlExprOp_StringConstant :
    case CdlExprOp_IntegerConstant :
    case CdlExprOp_DoubleConstant :
    {
        result = subexpr.constants;
        break;
    }
    case CdlExprOp_Reference :
    {
        // This expression may be happening in the context of a particular
        // property. If so then the destination may or may not be resolved,
        // and this is significant in the context of loading and unloading.
        // Alternatively this expression may be being evaluated inside
        // some Tcl code, with no particular context.
        CdlNode destination = 0;
        if (0 != context.property) {
            // There is a property, use the bound/unbound reference.
            destination = expr->references[subexpr.reference_index].get_destination();
        } else {
            // The destination name can be retrieved, but we still need some
            // way of resolving it.
            if (0 != context.toplevel) {
                std::string destination_name = expr->references[subexpr.reference_index].get_destination_name();
                destination = context.toplevel->lookup(destination_name);
            }
        }
        if (0 == destination) {
            // There are two ways of handling this.
            //   1) throw an eval exception, which will usually result
            //      in a new conflict object
            //   2) substitute a value of 0.
            // There should already be a conflict object for an
            // unresolved reference, and having two conflicts for
            // essentially the same error is not useful. Using a value
            // of 0 allows things to continue for a bit longer. It is
            // consistent with active vs. inactive values, gives
            // basically the right result for "requires" properties,
            // and so on.
            //
            // For now option (2) has it, but this decision may be
            // reversed in future.
            result = false;
        } else {
            CdlValuable valuable = dynamic_cast<CdlValuable>(destination);
            if (0 == valuable) {
                // This is a serious problem, an exception is warranted.
                throw CdlEvalException("The expression references `" + destination->get_class_name() + " " +
                                       destination->get_name() + "' which does not have a value.");
            } else {
                CdlSimpleValue::eval_valuable(context, valuable, result);
            }
        }
        break;
    }
    case CdlExprOp_Negate :
    {
        // Unary -. Evaluate the target. If it is numeric, fine. Otherwise
        // an error is warranted.
        evaluate_subexpr(context, expr, subexpr.lhs_index, result);
        if (result.has_integer_value()) {
            result.set_integer_value(-1 * result.get_integer_value());
        } else if (result.has_double_value()) {
            result.set_double_value(-1.0 * result.get_double_value());
        } else {
            throw CdlEvalException("Attempt to negate non-numeric value `" + result.get_value() + "'.");
        }
        break;
    }
    case CdlExprOp_Plus :
    {
        // Unary +. Essentially this just checks that the current value is numeric.
        evaluate_subexpr(context, expr, subexpr.lhs_index, result);
        if ((!result.has_integer_value()) && (!result.has_double_value())) {
            throw CdlEvalException("Attempt to apply unary + operator to non-numeric value `" + result.get_value() + "'.");
        }
        break;
    }
    case CdlExprOp_LogicalNot :
    {
        // !x
        evaluate_subexpr(context, expr, subexpr.lhs_index, result);
        if (result.get_bool_value()) {
            result = false;;
        } else {
            result = true;
        }
        result.set_value_format(CdlValueFormat_Default);
        break;
    }
    case CdlExprOp_BitNot :
    {
        // ~x. The operand must be an integer value.
        evaluate_subexpr(context, expr, subexpr.lhs_index, result);
        if (result.has_integer_value()) {
            cdl_int tmp = result.get_integer_value();
            result = ~tmp;
        } else {
            throw CdlEvalException("Attempt to apply unary ~ operator to non-integer value `" + result.get_value() + "'.");
        }
        break;
    }
    case CdlExprOp_Indirect :
    {
        // *x. The operand must evaluate to a string, and that string should be
        // the name of a CdlValuable object.
        CdlNode destination = 0;
        evaluate_subexpr(context, expr, subexpr.lhs_index, result);
        std::string name = result.get_value();
        
        if (0 != context.toplevel) {
            destination = context.toplevel->lookup(name);
        } else {
            CYG_FAIL("This situation should probably never happen.");
        }
        
        if (0 == destination) {
            throw CdlEvalException("Attempt to apply unary indirection operator * to `" + name +
                                   "', which is not the name of a known CDL entity.");
        } else {
            CdlValuable valuable = dynamic_cast<CdlValuable>(destination);
            if (0 == valuable) {
                throw CdlEvalException("Attempt to apply unary indirection operator * to `" + name +
                                       "', which does not have a value.");
            } else {
                CdlSimpleValue::eval_valuable(context, valuable, result);
            }
        }
        break;
    }
    case CdlExprOp_Active :
    {
        // ?x. If x is currently unresolved then default to 0.
        // See the CdlExprOp_Reference code above for a similar case.
        CdlNode destination = 0;
        if (0 != context.property) {
            destination =  expr->references[subexpr.reference_index].get_destination();
        } else {
            if (0 != context.toplevel) {
                std::string destination_name = expr->references[subexpr.reference_index].get_destination_name();
                destination = context.toplevel->lookup(destination_name);
            }
        }

        bool active = false;
        if ((0 != destination) && context.transaction->is_active(destination)) {
            active = true;
        }
        if (active) {
            result = true;
        } else {
            result = false;
        }
        break;
    }
    case CdlExprOp_Multiply :
    {
        // x * y. For now this only makes sense for numerical data,
        // but it is possible to mix and match integer and double
        // precision data.
        //
        // Strictly speaking the rhs need only be evaluated if it
        // is known that the lhs is numeric.
        CdlSimpleValue lhs;
        CdlSimpleValue rhs;
        evaluate_subexpr(context, expr, subexpr.lhs_index, lhs);
        evaluate_subexpr(context, expr, subexpr.rhs_index, rhs);
        if ((!(lhs.has_integer_value() || lhs.has_double_value())) ||
            (!(rhs.has_integer_value() || rhs.has_double_value()))) {
            throw CdlEvalException("Attempt to multiply non-numerical values: `" + lhs.get_value() + "' * `" +
                                   rhs.get_value() + "'.");
        }
        if (lhs.has_integer_value() && rhs.has_integer_value()) {
            result = lhs.get_integer_value() * rhs.get_integer_value();
        } else {
            result = lhs.get_double_value() * rhs.get_double_value();
        }
        result.set_value_format(lhs, rhs);
        break;
    }
    case CdlExprOp_Divide :
    {
        // x / y. Basically the same as multiplication, apart from a check for
        // division by zero.
        CdlSimpleValue lhs;
        CdlSimpleValue rhs;
        evaluate_subexpr(context, expr, subexpr.lhs_index, lhs);
        evaluate_subexpr(context, expr, subexpr.rhs_index, rhs);
        if ((!(lhs.has_integer_value() || lhs.has_double_value())) ||
            (!(rhs.has_integer_value() || rhs.has_double_value()))) {
            throw CdlEvalException("Attempt to divide non-numerical values: `" + lhs.get_value() + "' / `" +
                                   rhs.get_value() + "'.");
        }
        if (lhs.has_integer_value() && rhs.has_integer_value()) {
            cdl_int rhs_val = rhs.get_integer_value();
            if (0 == rhs_val) {
                throw CdlEvalException("Division by zero error: `" + lhs.get_value() + "' / `" + rhs.get_value() + "'.");
            } else {
                result = lhs.get_integer_value() / rhs_val;
            }
        } else {
            double rhs_val = rhs.get_double_value();
            if (0.0 == rhs_val) {
                throw CdlEvalException("Division by zero error: `" + lhs.get_value() + "' / `" + rhs.get_value() + "'.");
            }
            result = lhs.get_double_value() / rhs_val;
        }
        result.set_value_format(lhs, rhs);
        break;
    }
    case CdlExprOp_Remainder :
    {
        // x % y. Both operands must be integral.
        CdlSimpleValue lhs;
        CdlSimpleValue rhs;
        evaluate_subexpr(context, expr, subexpr.lhs_index, lhs);
        evaluate_subexpr(context, expr, subexpr.rhs_index, rhs);
        if (!(lhs.has_integer_value() && rhs.has_integer_value())) {
            throw CdlEvalException("Attempt to use the remainder operator on non integral data: `" +
                                   lhs.get_value() + "' % `" + rhs.get_value() + "'.");
        }
        cdl_int rhs_val = rhs.get_integer_value();
        if (0 == rhs_val) {
            throw CdlEvalException("Division by zero error: `" + lhs.get_value() + "' % `" + rhs.get_value() + "'.");
        }
        result = lhs.get_integer_value() % rhs_val;
        result.set_value_format(lhs, rhs);
        break;
    }
    case CdlExprOp_Add :
    {
        // x + y. For now this only makes sense for numerical data,
        // but it is possible to mix and match integer and double
        // precision data. Arguably for string data this operator
        // should mean concatenation, but it would probably be
        // safer to have a separate operator for that.
        //
        // Strictly speaking the rhs need only be evaluated if it
        // is known that the lhs is numeric.
        CdlSimpleValue lhs;
        CdlSimpleValue rhs;
        evaluate_subexpr(context, expr, subexpr.lhs_index, lhs);
        evaluate_subexpr(context, expr, subexpr.rhs_index, rhs);
        if ((!(lhs.has_integer_value() || lhs.has_double_value())) ||
            (!(rhs.has_integer_value() || rhs.has_double_value()))) {
            throw CdlEvalException("Attempt to add non-numerical values: `" + lhs.get_value() + "' + `" +
                                   rhs.get_value() + "'.");
        }
        if (lhs.has_integer_value() && rhs.has_integer_value()) {
            result = lhs.get_integer_value() + rhs.get_integer_value();
        } else {
            result = lhs.get_double_value() + rhs.get_double_value();
        }
        result.set_value_format(lhs, rhs);
        break;
    }
    case CdlExprOp_Subtract :
    {
        // x - y. Again only numerical data is supported for now.
        CdlSimpleValue lhs;
        CdlSimpleValue rhs;
        evaluate_subexpr(context, expr, subexpr.lhs_index, lhs);
        evaluate_subexpr(context, expr, subexpr.rhs_index, rhs);
        if ((!(lhs.has_integer_value() || lhs.has_double_value())) ||
            (!(rhs.has_integer_value() || rhs.has_double_value()))) {
            throw CdlEvalException("Attempt to subtract non-numerical values: `" + lhs.get_value() + "' - `" +
                                   rhs.get_value() + "'.");
        }
        if (lhs.has_integer_value() && rhs.has_integer_value()) {
            result = lhs.get_integer_value() - rhs.get_integer_value();
        } else {
            result = lhs.get_double_value() - rhs.get_double_value();
        }
        result.set_value_format(lhs, rhs);
        break;
    }
    case CdlExprOp_LeftShift :
    {
        // x << y. Both operands must be integral. For now there is no
        // check on the value of y.
        CdlSimpleValue lhs;
        CdlSimpleValue rhs;
        evaluate_subexpr(context, expr, subexpr.lhs_index, lhs);
        evaluate_subexpr(context, expr, subexpr.rhs_index, rhs);
        if (!(lhs.has_integer_value() && rhs.has_integer_value())) {
            throw CdlEvalException("Attempt to use the left-shift operator on non integral data: `" +
                                   lhs.get_value() + "' << `" + rhs.get_value() + "'.");
        }
        result = lhs.get_integer_value() << rhs.get_integer_value();
        result.set_value_format(lhs, rhs);
        break;
    }
    case CdlExprOp_RightShift :
    {
        // x >> y. Both operands must be integral. For now there is no
        // check on the value of y.
        CdlSimpleValue lhs;
        CdlSimpleValue rhs;
        evaluate_subexpr(context, expr, subexpr.lhs_index, lhs);
        evaluate_subexpr(context, expr, subexpr.rhs_index, rhs);
        if (!(lhs.has_integer_value() && rhs.has_integer_value())) {
            throw CdlEvalException("Attempt to use the right-shift operator on non integral data: `" +
                                   lhs.get_value() + "' >> `" + rhs.get_value() + "'.");
        }
        result = lhs.get_integer_value() >> rhs.get_integer_value();
        result.set_value_format(lhs, rhs);
        break;
    }
    case CdlExprOp_LessThan :
    case CdlExprOp_LessEqual :
    case CdlExprOp_GreaterThan :
    case CdlExprOp_GreaterEqual :
    {
        // x < y, and similar comparison operators. These share
        // sufficient code to warrant a common implementation. Only
        // numerical data is supported for now. These operator could
        // be interpreted as e.g. substring operations, but arguably
        // separate operators would be better for that.
        CdlSimpleValue lhs;
        CdlSimpleValue rhs;
        evaluate_subexpr(context, expr, subexpr.lhs_index, lhs);
        evaluate_subexpr(context, expr, subexpr.rhs_index, rhs);
        if ((!(lhs.has_integer_value() || lhs.has_double_value())) ||
            (!(rhs.has_integer_value() || rhs.has_double_value()))) {
            
            std::string op_str =
                (CdlExprOp_LessThan    == subexpr.op) ? "<" :
                (CdlExprOp_LessEqual   == subexpr.op) ? "<=" :
                (CdlExprOp_GreaterThan == subexpr.op) ? ">" : ">=";

            throw CdlEvalException("Attempt to compare non-numerical values: `" + lhs.get_value() +
                                   "' " + op_str + " `" + rhs.get_value() + "'.");
        }
        bool val = false;
        if (lhs.has_integer_value() && rhs.has_integer_value()) {
            cdl_int lhs_val = lhs.get_integer_value();
            cdl_int rhs_val = rhs.get_i